Canada

Dogs are a particularly useful model for heart problems in humans because they naturally get several of the same conditions and diseases humans do. You can try to create genetic variants of mice to have these conditions but it’s not nearly as good as a species that naturally experiences the condition. You may waste hundreds of mouse lives for poor quality research that way.

All studies involving animals require ethical approval involving a detailed assessment of the protocol by a committee that must include veterinarians, managers of the facility (not the lab members but outside of the research team), technicians who work directly with the animals, other researchers doing unrelated work, and a community member otherwise uninvolved in research at all. This is just for the ethical approval, they will also have to go through scientific merit evaluation by a different committee before this step. They must lay out exactly what they are doing and why it is necessary and how they are mitigating pain and distress. They may be under anesthesia for the entire heart attack, and then euthanized without waking up, or receive painkillers and be monitored constantly by a veterinarian. If they don’t do this, the work wont happen, and results wont be publishable either. Without being at that meeting we can’t know the exact technical justification, but there is a very strict process to follow and often everyone has more feelings about it when they are companion animals and they receive a lot of scrutiny.

I’m not all for animal research, some of it is poorly done and wasteful and doesn’t have any practical use. Or the data suffers from human incompetence. But a lot of it does help humans and animals. And there is a lot more tendency to intervene on pain and distress than you’d think - a distressed animal with no pain mitigation is not a good representation for your average human receiving treatment for something at a hospital. Your average local veterinary clinic almost certainly sees far worse cases of neglect and festering horrifying injuries and disease at the hands of incompetent dog owners than a study like this would ever produce.